Chemically bound hydrophobic modification in hydrogel surface layer using poly(N-vinylamide)s.

The novel hydrophobic surface modification of hydrogel structure, referred to as organohydrogel, was firstly achieved through the utilization of poly(N -vinylamide)s hydrogels, taking advantage of the property of polycation precursor. Following the shrinkage of poly(N -acetamide- co - N -vinylformamide), only the surface moiety was subjected to hydrolysis. Subsequently, a radical initiator was chemically tethered to the amino groups on the hydrogel surface to facilitate atom transfer radical polymerization (ATRP) of hydrophobic monomer, phenylethylacrylate. Hydrophobic layer characteristics were differentiated by varying hydrolysis time (x t) and ATRP time (y t), resulting in the creation of hydrophobic surface-modified gel (HSMgel). All HSMgels resulted in stable swelling ratio (S.R.) regardless of y t. The contact angle of water droplets increased gradually with both increasing x t and y t , from 17.6° to 91.9°, while maintaining a relatively constant S.R. The drying process of hydrophobic surface-modified HSMgels was accelerated, while that of precursor hydrophilic gels was delayed. These unique properties stemmed from the chemical structure of poly(N -vinylamide)s, which led to the formation of a chemically bound hydrophobic layer within the hydrogels. [Display omitted] • Surface modification of poly (N -vinylamide) hydrogels. • Hydrophobic modification on hydrogel. • ATRP approach enable to control hydrophobic layer on hydrogels. [ABSTRACT FROM AUTHOR]